This invention relates to entries for optical fibres to enclosures.
The invention is more particularly concerned with reducing the transmission of electromagnetic interference where a fibre-optic cable enters an enclosure, such as, at a connector.
The use of fibre-optic cables reduces the amount of electromagnetic interference supplied to and from enclosures via the cables. The enclosures themselves may also be screened further to reduce interference. Such enclosures, however, are not entirely immune from interference because the entry point of the cable to the enclosure is an aperture of the order of wavelengths in size at microwave frequencies. Where the entry to the enclosure is in the form of a connector, each fibre of the cable will generally be terminated by a metal ferrule which each act as an antenna, coupling microwave energy through the aperture into the interior of the enclosure. This problem can be increased where the entry aperture to the enclosure is filled with a dielectric material, such as a glass or polymer, because this has the effect of increasing the size of the aperture electrically and thereby increasing the range of frequencies that can enter the enclosure.